Onwa Marine Electronics KR-12X8 - Manual (Page 24)

Tip for adjusting the A/C SEA
A common mistake is to over-adjust the circuit so all the clutter is removed. As
an example set up for maximum STC. You will see how the center of the display
becomes dark. This dark zone can be dangerous (targets may be missed),
especially if the sensitivity is not properly adjusted. Always leave a little clutter
visible on the display to be sure weak echoes will not be suppressed. If there is
no clutter visible on the display, turn off the circuit.
2.14 Apply the A/C RAIN (reducing rain clutter)
The vertical beamwidth of the antenna is designed to see surface targets even
when the ship is rolling. However, by this design the unit will also detect rain
clutter (rain, snow, hail, etc.) in the same manner as normal targets. Figure 2-5
Appearance of rain clutter A/C RAIN control adjusted;
rain clutter suppressed.
Figure 2-5 Effect of A/C RAIN
Adjusting A/C RAIN
When rain clutter masks echoes, adjust the [A/C RAIN] Control, This control spl-
its up these unwanted echoes into a speckled pattem, making recognition of solid
targets easier.
Shows the appearance of rain clutter on the Display.
Note: In addition to reducing clutter, the [A/C RAIN] control can be used in fine
weather to clarify the picture when navigating in confined waters. However, with
the circuit activated the receiver is less sensitive. Therefore, turn off the circuit
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when its function is not used.